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Discussion Starter #1
I am looking at buying a 4720 with 800 hours.
I noticed after it warmed up that the tire would jerk a bit with a slight shudder.
Is this common for this machine or is this an issue that may be larger than I want to tackle?

Anyone have a service manual for this machine? I am wondering if there is any trouble shooting.
 

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When do you notice the shudder? When sitting neutral or when going forward, reverse, changing direction, etc?
 
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Discussion Starter #4
When do you notice the shudder? When sitting neutral or when going forward, reverse, changing direction, etc?
So I was looking at the front right tire. I notice it when sitting still. I can also feel it a bit in the steering wheel when the rpms are up. Kind of a pumping feel that doesn't coincide with the engine.

I just don't want to buy a machine that has a major hydraulic pump issue.
 

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So I was looking at the front right tire. I notice it when sitting still. I can also feel it a bit in the steering wheel when the rpms are up. Kind of a pumping feel that doesn't coincide with the engine.

I just don't want to buy a machine that has a major hydraulic pump issue.
Hmmm... I’m not sure what would cause just the right front tire to jerk and shudder without any of the other tires moving. With a hydro tractor the pump can’t make a wheel jerk on its own. The pump supplies power to the transmission which then controls all of the wheels.

Since on 4WD tractors only one front wheel is driven, I have to assume the front drive shaft is jerking and shuddering at the same time.
 
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Hmmm... I’m not sure what would cause just the right front tire to jerk and shudder without any of the other tires moving. With a hydro tractor the pump can’t make a wheel jerk on its own. The pump supplies power to the transmission which then controls all of the wheels.
The 4720 has 2 hydro pumps. One for drive power and one for power steering. It's possible that the power steering pump/circuit/linkage is what is causing the shuddering that he's seeing. Since he's only seeing it on one wheel, I'd suspect that the issue isn't with the steering pump itself. But it could be related to a linkage issue with that particular front wheel.
 
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Hmmm... I’m not sure what would cause just the right front tire to jerk and shudder without any of the other tires moving. With a hydro tractor the pump can’t make a wheel jerk on its own. The pump supplies power to the transmission which then controls all of the wheels.

Since on 4WD tractors only one front wheel is driven, I have to assume the front drive shaft is jerking and shuddering at the same time.
Well I was only looking at the front right. I could feel the machine move a bit. That's why I looked at the wheel. From what you indicate would it then be more of a transmission movement? Do any of you have this machine? Is it normal to feel a pulsation in the steering wheel?

Owner indicated that the 4720 has a loud transmission.

I think I might go back and play around with it again.
 

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Is it normal to feel a pulsation in the steering wheel?
I don't think it is ever normal for any machine to have a pulsing in the steering.

That said, I have seen people with this sort of issue on a 4720 before. The 4720 has a hydro fluid filter on the return line from the power steering circuit. If that filter gets plugged up, you get some jerking in the power steering system because teh plugged up filter mucks with the circuit pressure. The filter is under the floorboard on the left-hand side of the machine. You might look under there and see if it looks like that filter has ever been changed. The "solution" might be as simple as changing that filter.
 

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I don't think it is ever normal for any machine to have a pulsing in the steering.

That said, I have seen people with this sort of issue on a 4720 before. The 4720 has a hydro fluid filter on the return line from the power steering circuit. If that filter gets plugged up, you get some jerking in the power steering system because teh plugged up filter mucks with the circuit pressure. The filter is under the floorboard on the left-hand side of the machine. You might look under there and see if it looks like that filter has ever been changed. The "solution" might be as simple as changing that filter.
This sounds like a great place to start.

If that return filter is plugging up it could be the cause of the pulsating. Then, if one wheel only is jerking, it sounds like there may be a little wear in the tie rod or hydraulic piston end. If the filter change would stop the pulsating the slightly worn tie rod or end won’t be an issue.
 
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This sounds like a great place to start.

If that return filter is plugging up it could be the cause of the pulsating. Then, if one wheel only is jerking, it sounds like there may be a little wear in the tie rod or hydraulic piston end. If the filter change would stop the pulsating the slightly worn tie rod or end won’t be an issue.
It might be a good time to ask if the wheel is jerking back and forth (aka steering linkage) or is it jerking forward / backward as in rotational movement. I could see the explanations offered applying to a steering movement but not for rotational movement.

Too bad the OP doesn't have a video showing the condition.
 

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Discussion Starter #11
It might be a good time to ask if the wheel is jerking back and forth (aka steering linkage) or is it jerking forward / backward as in rotational movement. I could see the explanations offered applying to a steering movement but not for rotational movement.

Too bad the OP doesn't have a video showing the condition.
Thanks guys for the insight. I will look at it tonight and if it does it again take a video and post.

I will check out the filter that was indicated. Anyone know if that is something I can take out without doing a complete fluid change?
 

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Thanks guys for the insight. I will look at it tonight and if it does it again take a video and post.

I will check out the filter that was indicated. Anyone know if that is something I can take out without doing a complete fluid change?
You can service that filter without losing a whole lot of fluid. It would be beneficial to have a helper to hold their finger over the line while you clean the filter. I use starting fluid—the buzz is better than brake parts cleaner.
 

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Just had another thought while eating lunch...

Since you are going back to look at the tractor again -

While it is running check to be sure the 3-point hitch isn’t jumping every so often. Sometimes when the feedback control is out of adjustment the hitch will jump every so often - even just a slight bit. If it does this you would likely feel it in the steering wheel and could also make the power steering cylinder jump ever so slightly.

A long shot I know...but stranger things have happened.....only takes a second to check and doesn’t cost anything.
 

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Just had another thought while eating lunch...

Since you are going back to look at the tractor again -

While it is running check to be sure the 3-point hitch isn’t jumping every so often. Sometimes when the feedback control is out of adjustment the hitch will jump every so often - even just a slight bit. If it does this you would likely feel it in the steering wheel and could also make the power steering cylinder jump ever so slightly.

A long shot I know...but stranger things have happened.....only takes a second to check and doesn’t cost anything.

I took another look at it but decided its safer for my investment to just pass on a potential issue as its a large investment. Let the owner fix it. It wasn't doing it yesterday though. 2006 $21,000 with 800 hrs is a lot of money. I will stick with my JD 4100 till I find a similar deal with no issues.

thanks for all your help.
 

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I took another look at it but decided its safer for my investment to just pass on a potential issue as its a large investment. Let the owner fix it. It wasn't doing it yesterday though. 2006 $21,000 with 800 hrs is a lot of money. I will stick with my JD 4100 till I find a similar deal with no issues.

thanks for all your help.
Probably a good move. If you bought it, even if it wasn’t doing it, it would always be in the back of your mind.

You will know when you come upon the perfect tractor for yourself.
 
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